Failure of the physical servers on which Directory Server or Directory Proxy Server are
running

Load balancer failures

Storage subsystem failures

Power supply failures

Failure at the network level can be mitigated by having redundant network
components. When designing your deployment, consider having redundant components
for the following:

Internet connection

Network interface card

Network cabling

Network switches

Gateways and routers

You can mitigate the load balancer as an SPOF by including a redundant
load balancer in your architecture.

In the event of database corruption, you must have a database failover
strategy to ensure availability. You can mitigate against SPOFs in the storage
subsystem by using redundant server controllers. You can also use redundant
cabling between controllers and storage subsystems, redundant storage subsystem
controllers, or redundant arrays of independent disks.

If you have only one power supply, loss of this supply could make your
entire service unavailable. To prevent this situation, consider providing
redundant power supplies for hardware, where possible, and diversifying power
sources. Additional methods of mitigating SPOFs in the power supply include
using surge protectors, multiple power providers, and local battery backups,
and generating power locally.

Failure of an entire data center can occur if, for example, a natural
disaster strikes a particular geographic region. In this instance, a well-designed
multiple data center replication topology can prevent an entire distributed
directory service from becoming unavailable. For more information, see Using Replication and Redundancy for High Availability.